On drum brake systems, the wheel cylinders are always fastened firmly to the ________.

In drum brake systems, the wheel cylinders are securely fastened to the brake backing plate. This design is critical because the brake backing plate acts as a structural base for the drum brake assembly, providing stability for the wheel cylinder as well as the other components, such as the brake shoes and springs. The wheel cylinder is responsible for converting hydraulic pressure into mechanical force, pushing the brake shoes against the drum to create friction and ultimately slow down or stop the vehicle. Proper attachment to the backing plate ensures that the wheel cylinder functions efficiently and maintains the correct alignment during the braking process.

The other options do not serve as the mounting point for the wheel cylinders in a drum brake system. The anchor typically refers to a fixed point for the brake shoes but doesn’t provide the necessary structure for the wheel cylinder. The hub is the part of the wheel assembly that connects to the axle and does not directly relate to the brake mechanism. The wheel well refers to the area of the vehicle that houses the wheel and does not have any connection with the functioning of the brake system components.